Powered impact tools



Dec. 14, 1965 Tosi-uo MIKIYA POWERED IMPACT TOOLS 5 Sheets-Sheet 1 FiledMarch 26, 1965 POWERED IMPACT TOOLS INVENTOR rdff//a M/,f//1/4 Dec. 14,1965 Tosi-no MlKlYA POWERED IMPACT TOOLS 5 Sheets-Sheet 5 Filed March26, 1965 N l: 1 Mm/2.1

v INVENTOR raf/Wa /W/A//y 3,223,182 POWERED IMPACT TOOLS Toshio Mikiya,Tokyo, Japan, assigner to Nitto Kohki Co., Ltd., Tokyo, Japan, acorporation of Japan Filed Mar. 26, 1965, Ser. No, 444,510

Claims priority, application Japan, Aug. 7, 1962,

37/ 32,572 4 Claims. (Cl. 173-114) This application is acontinuation-in-part of copending application Serial No. 250,858 tiledon January 1l, 1963, now abandoned.

This invention relates to powered impacted tools actuated by compressedair, for driving perforated needles, chisels and other tool elementsand, more particularly, to pneumatic chisels having improved mechanismfo-r supporting and imparting impact blows to the chisel elements Iofsuch a device.

While the following specification is principally directed to thestructure of pneumatic chisels incorporating the present invention, itwill be understood that the invention is applicable to other poweredimpact tools incorporating other tool elements for effecting desiredwork functions.

In conventional pneumatic chisels, the chisel elements are drivenforward by the force of compressed air and returned to normal positionby the force of a spring that has been` compressed by the forwardmovement of the chisel elements. Consequently, the power for driving thechisel elements is partly consumed for com-pressing the returnspring,resulting in the loss of impact energy. Moreover, such a mechanicalspring is apt to be damaged or to deteriorate rather quickly since it issubjected to repeated compression and release, with high frequency.

In certain types of pneumatic chisels, the impact blows of a hammerpiston are transmitted directly to the chisel elements, so that thechisel must be manually and firmly pressed against the work surface. Theoperation of such chisel requires bodily strength. Moreover, ordinarypneumatic chisels do not work satisfactorily `on `curved or unevensurfaces.

One of the objects of the present invention, therefore, is to permit theconstruction of a pneumatic chisel in which the well-known chiselreturn-spring is eliminated.

It is another object of the invention tio provide an improved pneumaticchisel comprising an air cylinder having a hammering piston, athrottle-anvil and a second piston which elements pneumaticallycooperate with one another for imparting impact blows to a bundle ofchisel elements.

It is a still further `object of the invention to improve theconstruction o-f the chisel elements, or the bundle o-f needles of apneumatic chisel, as regards the manner of support thereof, so that theneedles are projected like bullets from the second piston.

A further object of the invention is to provide an improved driving andreturn device for pneumatic chisels which permits easy operation andwhich, when the ch-isels are pointed at a curved or uneven surface,positively adapts itself to such surface without having to press thechisel to direct the bundle of needles onto the work surface.

For other objects and for a better understanding of the invention,reference may be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIGURE l is a longitudinal sectional view of a preferred embodiment ofthe powered impact tool of the present invention, showing thehammer-piston and needle or chisel elements in their forward projectedpositions.

FIGURE 2 is a view similar to FIGURE 1, illustrating the positions ofthe respective elements of the tool immediately after actuation thereof;

te States Patent O ice FIGURES 3 and 4 are partial longitudinalsectional views corresponding to FIGURES l and 2 deleting, however,illustration of the valve mechanism of the tool, and showing theorientation of the elements of the device in successive stages of theoperation thereof; and

FIGURE 5 is a view similar to FIGURE 4, showing the device :actingagainst a curved work surface.

The powered impact tool hereof comprises an air cylinder including firstand second cylindrical segments which are coupled to one another andwhich contain longitudinally extending air conduits formed in theirwalls and having valve means for controlling the iiow of compressed airthereto. A hammer piston is slidably mounted in the iirst cylindricalsegment. Mechanism is provided for introducing compressed air from theair conduits peripherally of such piston and for exhausting air frombehind it to move the piston from a rst to a second position, andmechanism is provided for introducing compressed air behind the pistonto return it from the second to the rst position.

A tool holder is slidably mounted in the second cylindrical segment ofthe air cylinder, having a chamber formed in and extendinglongitudinally thereof. Further mechanism is provided for introducingcompressed air from the air conduits into such chamber to move it from arst position to a second position, for interrupting the flow lofcompressed air when the tool holder is disposed intermediate suchpositions and for exhausting the air from a chamber when the tool holderreaches the second position.

A plurality of tool elements are slidably received in the tool holderextending longitudinally yof and protruding from the air cylinder, suchelements being movable from a first position seated in the tool holder,when it is disposed in its iirst position, to a second position out ofseating engagement with the tool holder, and being movable from thesecond position back to such first position.

Slidably mounted in the second cylinder segment intermediate the hammerpiston and the tool holder is an anvil, which is movable by the too-lelements from a iirst position abutting the too-l holder to a secondposition spaced therefrom, and which is movable from such secondposition to its first position by the hammer piston. The anvil, duringmovement from its second to its first position, strikes the toolelements and projects them longitudinally relative to the tool holder toeffect the desired work functions.

Referring to the drawing, the powered impact tool or pneumatic chiselillustrated comprises a rear cylinder 1 and a front cylinder 2 joined bya closure member 3. Suitable packing rings 4 and 5 are located at thejuncture portions of the respective cylinders 1 and 2.

'Iihe rear cylinder 1 is internally threaded at 6 (see FIG- URES l and2) to receive a lcylinder head 7 having a valve element 8. The latterelement may be depressed by a manually operable lever 9 pivotallyconnected to the cylinder head 7 at 10. The valve includes a valvechamber 12 having a seat to -which the element 8 is normally urged by aspring 13 and a plug 14 threaded into the cylinder head 7. The valvechamber communicates with a nipple 11, which may be secured to an airhose or the like.

Extending longitudinally through the wall of the rear cylinder 1 are airsupply conduits 15, 15. Such conduits communicate with a longitudinalair conduit 16 in the wall of the front cylinder 2 through an annularchamber 17 dened at the juncture of the respective cylinders and sealedby the packing ring 4. The air conduits 15, 15 additionally communicatewith the valve chamber 12 at a port 18 through an annular space 19formed at the juncture of the cylinder head 7 and the rear cylinder 1.Packing ring 20 is provided between the cylinder head 7 and the innerwalls of the cylinder 1 for preventing escape of the compressed air fromthe annular space 19.

Mounted slidably within a chamber 21 defined in the rear cylinder is ahammer-piston 22 having an internal bore 23 opening at one end into therear cylinder chamber 21. The hammer-piston includes a cylindricalportion 24 projecting forwardly from, and of reduced diameter withrespect to, a cylindrical root portion 25 thereof.

The cylinder chamber 21 in which the hammer-piston 22 is received isprovided with aforward axial bore 26 and a main cylinder bore 28,separated by a step portion 33. When the hammer-piston 22 is disposed inthe rearward position of its stroke, with the reduced cylinder portion24 extending into a main cylinder bore 28, an annular space 27 isdefined therebetween (see FIGURES 2 and 3). The hammer-piston isprovided with ports 29 in the lower end of bore 23 thereof forcommunicating with such annular space 27 which is, in turn, connectedthrough ports 30 to the air `supply conduits -15, 15.

The rear cylinder 1 is also provided with an enlarged forward axial bore31 communicating with an exhaust port 32 formed in the wall of the frontcylinder 2. When the ham-mer-piston is disposed in the forward portionof its stroke, with the inlet ports 30 closed by the root portion 25thereof, the ports 29 of the bore 23 communicate with the atmospherethrough bore 31 and exhaust port 32.

The front cylinder 2 has an anvil 34 and a second piston or tool holder35 slidable therein, respectively. The tool holder, which is heavierthan the anvil 34, carries a number of needles 36 which are movable withrespect thereto and include enlargements 37 on their rear endspreventin-g disengagement of the needles from the holder 35.

The tool holder 35 has a hollow reduced cylindrical extension 38, theinterior of which communicates with the atmosphere and which is slidablyreceived in a neck portion 39 of the front cylinder 2. Above the neckportion, air passages 40, 40 are provided extending longitudinallythrough the walls of the tool holder. When the tool holder is disposedin the forward portion of its stroke (FIGURE 1) each of these airpassages 16 of the front cylinder 2 and is seated, at its opposite end,on a shoulder portion 42 of the front cylinder adjacent the neck portion39 thereof. When, on the other hand, the tool holder 35 is disposed inthe rearward portion of its stroke (FIGURE 3) the air passages 40, 40 donot communicate with passage 16 but communicate instead with theatmosphere through ports 43, 43 defined in the walls of extension 38 ofthe tool holder.

The front cylinder 2 has an opening 44 through which air may beexhausted from the space between anvil 34 and the tool holder 35 to theatmosphere` Additionally, a cover sleeve 45 is preferably provided forcovering the opening 44 and the above-mentioned exhaust port 32 toprotect the operator from the high pressure exhaust.

In operation, the lever 9 is depressed against the Valve spring 13(compare FIGURES l and 2) in order to feed compressed air into the airsupply conduits 15, and 16 of the rear and front cylinders 1 and 2. Thecompressed air supplied through inlet ports 30 is fed over the peripheryof root portion 25 of piston 22 into the annular region adjacent stepportion 33 of the cylinder chamber 21. The resulting air pressure forcesthe hammer-piston 22 rearwardly, or upwardly (viewing FIGURE 1), intothe successive positions illustrated in FIGURES 2 and 3 of the drawings.It will be noted that, while the compressed air introduced through ports30 is similarly fed to the portion of cylinder chamber 21 to the rear(above, viewing FIG- URE l) of the hammer-piston, no counter-pressure isproduced since the air is exhausted to the atmosphere through the pistonbore 23, ports 29 and exhaust port 32.

The compressed air is simultaneously fed into air passages 40, 40through port 41 from supply conduit 16, forcing the tool holder 35, theneedles 36 and the adjacent anvil 34 rearward from the position shown inFIGURE 1 4- to that illustrated in FIGURE 2. Shortly after initiatingmovement of the tool holder 35 the air passages 40, 40 are displaced outof communication with port 41 connected to the supply conduit 16,`cutting off flow of compressed air to passages 40, 40 and terminatingthe rearward movement of the tool holder when it reaches the positionillustrated in FIGURE 3. The anvil 35 and needles 36 are, as illustratedin FIGURES 2 and 3, simultaneously displaced from the heavier toolholder 35, after the initial rearward thrust thereof, by the force ofinertia.

When the hammer-piston 22 and tool holder 35 reach the end-s of theirrearward strokes (FIGURE 3) the forward strokes are automaticallyinitiated. Thus, when the hammer-piston reaches the end of its strokethe ports 29 thereof communicate with annular space 27, permitting theflow of compressed air from supply conduits 15, 15 through ports 30,space 27, ports 29 and bore 23 into the rear cylinder chamber 21.Continued flow of the compressed air stream initiates the forward, ordownward (viewing FIGURE 3), stroke of the piston 22 against the anvil34 which, in turn, imparts an impact blow to the needles 36 (FIGURES 4).The several needles 36 are thus driven forward to elfe-ct chiseling ofthe work surface.

Towards the end of the forward stroke of the anvil 34 (between thepositions illustrated in FIGURES 4 and l), the anvil strikes the toolholder 35, displacing the tool holder so that the ports 43, 43 of thecylindrical extension 38 thereof are closed by the neck portion 39 ofthe 'front cylinder 2. Sufficient air is thereby trapped in the spaceabove the shoulder portion 42 of the front cylinder 2 to provide an aircushion the effect of which is not, however, so large that issignicantly decreases the working force or power of the needles 36.

When the hammer-piston 22 reaches the end of its forward stroke theports 29 are placed in communication with exhaust port 32 through bore31, thereby exhausting the air from bore 23 of the piston and permittingthe return stroke to commence as described above. Additionally, when thetool holder 35 reaches the end of its forward stroke the air passages 40come into registry with port 41 communicating with air supply conduit16, effecting the return stroke of the holder, the needles 36 and theanvil 34. It will be noted that, while the anvil 34 acts dynamically onthe needles 36 during the forward stroke of the device, it imposes nopositive force opposing the rearward stroke of the tool holder 35 orneedles 36, since both axial ends of the anvil are exposed toatmospheric pressure through exhaust ports 32 and 44.

It will thus be noted that the plurality of needles 36 are thus actuatedrepeatedly with high speed toward the desired work surface, as long asthe operating lever 9 is depressed.

The pneumatic chisel of the invention is of light weight, easily handledand has many uses. Some of such uses are shot peening for metalsurfaces, chiseling out pipe channels, de-rusting and de-scaling,roughing up and cleaning concrete and masonry, etc., cleaning weldseams, roughing up for metalizing, cleaning casings, de-furring boilers,stripping paint, bitumen, etc., removing plaster, etc.

For certain uses of the pneumatic chisel, the needles 36, 36 should notbe pressed against the working surface. It is preferred to hold thechisel firmly at a proper distance from the work surface, so that thefloating needles act on the work surface like bullets. In this manner,as shown in FIGURE 5, the device may be utilized to act on curved oruneven surfaces.

It will be understood that various changes may be made in the embodimentof the powered impact tool described hereinabove without departing fromthe scope of the present invention; accordingly, it is intended that thepreceding description and the accompanying drawings are illustrative andshould not be considered in a limiting sense,

pressed air, which comprises.:

(a) an air cylinder comprising first and second cylindrical segmentscoupled to one another;

(b) air conduits formed in the walls of said air cylinder and extendinglongitudinally thereof;

(c) valve means connected to said air conduits for controlling the flowof compressed air thereto;

(d) a hammer-piston slidably mounted in said first cylindrical segment;

(e) means for introducing compressed air from said air conduitsperipherally of said piston and means for exhausting air from behindsaid piston when the piston is disposed in a first position, to effectmovement thereof to a second position;

(f) means for introducing compressed air from said air conduits behindsaid piston when it is disposed in said second position, to return thepiston to said first position;

(g) a tool holder slidably mounted in said second cylindrical segment;

(h) a chamber, formed in and extending longitudinally of said toolholder;

(i) means for introducing compressed air from said air conduits intosaid chamber to move the tool holder from a first position to a secondposition;

(j) means for interrupting the flow of compressed air from said airconduits into said chamber when the tool holder is disposed intermediatethe first and second positions thereof; Y

(k) means for exhausting the air from said chamber when the tool holderis disposed at said second position;

(l) a plurality of tool elements slidably received in said tool holderand extending longitudinally of and protruding from said air cylinder,said elements being movable from a first position seated in the toolholder, when it is disposed in its first position, to a second positionout of seating engagement with said tool holder, and being movable fromsaid second position back to said first position;

(m) an anvil slidably mounted in said second cylindrical segmentintermediate the hammer-piston and the tool hol-der, said anvil beingmovable by said tool elements from a first position abutting said toolholder to a second position spaced therefrom, and being movable from thesecond position to said first position by said hammer-piston; saidanvil, during movement from its second to its first position, strikingsaid tool elements and projecting them longitudinally relative to saidtool holder.

2. The powered impact tool as set forth in claim 1, in

which said tool holder includes a first hollow cylindrical segmentdefining a plurality of seats for receiving said tool elements forslidable movement relative thereto, said segment providing an annularchamber extending longitudinally of the tool hol-der in the wallsthereof and communicating at one end with a port extending through thewalls of the tool holder;

a second hollow cylindrical extension segment formed integrally withsaid first segment, the hollow interiors of said segments communicatingwith one another and said second segment defining annular ports forconnecting said hollow interiors with said annular chamber when the toolholder is disposed in the second position thereof;

and in which the second cylindrical segment slidably mounting the toolholder includes a first, expanded bore in which the first cylindricalsegment of the tool holder is mounted, said bore including means forcommunicating with the port in said first segment when the tool holderis disposed in its first position, for connecting said chamber with saidair conduits;

a second, restricted bore in which the cylindrical extension of the toolholder is slidably mounted, said second bore defining a port connectingthe hollow interior of the tool holder with the atmosphere.

3. The powered impact tool as set forth in claim 1, in

which said hammer-piston includes and in which the first cylindricalsegment in which said hammer-piston is slidably mounted denes a firstbore slidably mounting the root segment of the hammer-piston, the wallsof said bore defining ports extending -therethrough and communicatingwith said air con-duits;

a second bore slidably mounting the second segment of the hammer-piston;

expanded bore communicating with the atmosphere and communicating, inturn, with the ports defined in the walls of the second cylindricalsegment of the hammer-piston, when the piston is disposed in its firstposition; and

a step portion intermediate said bores, said step portion communicatingwith the ports defined in the walls of said first bore when the hammerpiston is disposed in said first position.

4. A powered impact tool to be activated by compressed air, whichcomprises:

(a) an air cylinder comprising first and second cylindrical segmentscoupled to one another;

(b) air conduits formed in the walls of said air cylinder and extendinglongitudinally thereof;

(c) valve means connected to said air conduits for controlling the flowof compressed air thereto;

(d) a hammer-piston 4slidably mounted in said rst cylindrical segmentfor movement between a first and a -second position, said hammer-pistoncomprising:

( 1) a first cylindrical root segment,

(2) a second cylindrical segment integral with said root segment andhaving a relatively restricted diameter with respect thereto, saidsegments defining a bore extending longitudinally of the piston andcommunicating at one end with the back of the piston adjacent to theroot segment and at the opposite end with ports defined in the walls ofsaid restricted cylindrical segment;

(e) the first cylindrical segment of the air cylinder providing:

(1) a first bore slidably mounting the root segment of thehammer-piston, the walls of said bore defining ports extendingtherethrough and communicating with said air conduits;

(2) a second bore slidably mounting the second segment of thehammer-piston;

(3) an expanded bore communicating with the atmosphere andcommunicating, in turn, with the ports defined in the Walls of thesecond cylindrical segment of the hammer-piston, when the piston isdisposed in its first position; and

(4) a step portion intermediate said first .and second bores, said stepportion communicating with the ports defined in the walls of said firstbore when the hammer-piston is disposed in said first position;

(f) a tool holder slidably mounted in the second cylindrical segment ofthe air cylinder for movement between a first and second position, saidtool holder including:

(1) a first hollow cylindrical segment defining a plurality of seats forreceiving the tool elements defined hereinafter for slidable movementrelative thereto, said segment vproviding an annular chamber extendinglongitudinally of the tool holder in the walls thereof and communicatingat one end with a port extending through the walls of the tool holder;

(2) a second hollow cylindrical extension segment formed integrally withsaid first segment, the hollow interior regions of said segmentscommunicating with one another and said second segment defining annularports for connecting `said interior regions with said annular chamberwhen the tool holder is disposed in the second position thereof;

(g) the second cylindrical segment of the air cylinder providing:

(1) a first expanded bore in which the first cylin- (h) a plurality oftool elements slidably received in said tool holder and extendinglongitudinally of and protruding from said air cylinder, said elementsbeing movable from a first position seated in the tool holder when i-tis disposed in its rst position, to a second position out of seatingengagement with said tool holder, and being movable from said secondposition back to said first position; and

(i) an anvil slidably mounted in said second cylindrical segmentintermediate the hammer-piston and the References Cited by theApplicant' UNITED STATES PATENTS drical segment of the tool holder ismounted, 842655 1/1907 Halfdsoeg' said bore including means forcommunicating 1076I246 10/1913 Smlth with the port in said first segmentwhen the 25 1,583,288 5/1926 Gflmantool holder is disposed in its firstposition, for 1,747,164 2/1930 DltSOn et aL connecting said chamber withsaid air conduits; 2,356,314 8/1944 Gray et al- (2) and a second,restricted bore in which the y 2,613,647 10/ 1952 Curtis.

cylindrical extension of the tool holder is slid- 2,672,129 3/1954Fischer. ably mounted, said second bore defining ya port 3()y 2,672,6773/ 1954 Von Arx.

connecting the hollow interior of the tool holder with the atmosphere;MILTON KAUFMAN, Primary Examiner.

1. A POWERED IMPACT TOOL TO BE ACTIVATED BY COMPRESSED AIR, WHICHCOMPRISES: (A) AN AIR CYLINDER COMPRISING FIRST AND SECOND CYLINDRICALSEGMENTS COUPLED TO ONE ANOTHER; (B) AIR CONDUITS FORMED IN THE WALLS OFSAID AIR CYLINDER AND EXTENDING LONGITUDINALLY THEREOF; (C) VALVE MEANSCONNECTED TO SAID AIR CONDUITS FOR CONTROLLING THE FLOW OF COMPRESSEDAIR THERETO; (D) A HAMMER-PISTON SLIDABLY MOUNTED IN SAID FIRSTCYLINDRICAL SEGMENT; (E) MEANS FOR INTRODUCING COMPRESSED AIR FROM SAIDAIR CONDUITS PERIPHERALLY OF SAID PISTON AND MEANS FOR EXHAUSTING AIRFROM BEHIND SAID PISTON WHEN THE PISTON IS DISPOSED IN A FIRST POSITION,TO EFFECT MOVEMENT THEREOF TO A SECOND POSITION; (F) MEANS FORINTRODUCING COMPRESSED AIR FROM SAID AIR CONDUITS BEHIND SAID PISTONWHEN IT IS DISPOSED IN SAID SECOND POSITION, TO RETURN THE PISTON TOSAID FIRST POSITION; (G) A TOOL HOLDER SLIDABLY MOUNTED IN SAID SECONDCYLINDRICAL SEGMENT; (H) A CHAMBER, FORMED IN AND EXTENDINGLONGITUDINALLY OF SAID TOOL HOLDER; (I) MEANS FOR INTRODUCING COMPRESSEDAIR FROM SAID AIR CONDUITS INTO SAID CHAMBER TO MOVE THE TOOL HOLDERFROM A FIRST POSITION TO A SECOND POSITION; (J) MEANS FOR INTERRUPTINGTHE FLOW OF COMPRESSED AIR FROM SAID AIR CONDUITS INTO SAID CHAMBER WHENTHE TOOL HOLDER IS DISPOSED INTERMEDIATE THE FIRST AND SECOND POSITIONSTHEREOF; (K) MEANS FOR EXHAUSTING THE AIR FROM SAID CHAMBER WHEN THETOOL HOLDER IS DISPOSED AT SAID SECOND POSITION; (L) A PLURALITY OF TOOLELEMENTS SLIDABLY RECEIVED IN SAID TOOL HOLDER AND EXTENDINGLONGITUDINALLY OF AND PROTRUDING FROM SAID AIR CYLINDER, SAID ELEMENTSBEING MOVABLE FROM A FIRST POSITION SEATED IN THE TOOL HOLDER, WHEN ITIS DISPOSED IN ITS FIRST POSITION, TO A SECOND POSITION OUT OF SEATINGENGAGEMENT WITH SAID TOOL HOLDER, AND BEING MOVABLE FROM SAID SECONDPOSITION BACK TO SAID FIRST POSITION; (M) AN ANVIL SLIDABLY MOUNTED INSAID SECOND CYLINDRICAL SEGMENT INTERMEDIATE THE HAMMER-PISTON AND THETOOL HOLDER, SAID ANVIL BEING MOVABLE BY SAID TOOL ELEMENTS FROM A FIRSTPOSITION ABUTTING SAID TOOL HOLDER TO A SECOND POSITION SPACEDTHEREFROM, AND BEING MOVABLE FROM THE SECOND POSITION TO SAID FIRSTPOSITION BY SAID HAMMER-PISTON; SAID ANVIL, DURING MOVEMENT FROM ITSSECOND TO ITS FIRST POSITION, STRIKING SAID TOOL ELEMENTS AND PROJECTINGTHEM LONGITUDINALLY RELATIVE TO SAID TOOL HOLDER.